Effects of the B←N unit on the energy level of conjugated small molecule were investigated by synthesizing a new small molecule BPDPP (3,8-bis(5-(2,5-dioctyl-3,6-dioxo-4-(thiophen-2-yl)-2,3,5,6-tetrahydropyrrolo[3,4-c]pyrrol-1-yl)-thiophen-2-yl)-6,6-dioctyl-6H-benzo[3,4] [1,2]azaborolo[1,5-a]pyridin-5-ium-6-uide) via Suzuki coupling. For comparison, CPDPP (6,6′-(5,5′-(9,9-dioctyl-9H-fluorene-2,7-diyl)bis(thiophene-5,2-diyl))bis(2,5-dioctyl-3-(thiophen-2-yl)pyrrolo[3,4-c] pyrrole-1,4(2H,5H)-dione)) having the same chemical structure with BPDPP except the B←N unit is synthesized through the same coupling reaction. Absorption spectra and cyclovoltammetry analysis for these small molecules revealed that the B←N unit reduces the band gap of BPDPP by maintaining large oxidation potential. As a result, the blend film of BPDPP and PC₇₁BM maintained 87.4% of the initial absorption intensity after 1sun light soaking test for 315 h. The photo stability of the BPDPP is significantly higher than the blend film of P3HT: PC₇₁BM, which maintained only 19.8% of the initial absorption intensity only after light soaking for 23 h.

通过合成新的小分子BPDPP（3,8-bis（5-（2,5- dioctyl -3,6-dioxo-4-（thiophen））来研究B←N单元对共轭小分子能级的影响-2-基）-2,3,5,6-四氢吡咯并[3,4-c]吡咯-1-基）-噻吩-2-基）-6,6-二辛基-6H-苯并[3,4]通过铃木偶联的[1,2]氮杂硼杂环[[1,5-a]吡啶基-5-基-6-脲）。为了比较，CPDPP（6,6'-（5,5'-（9,9-二辛基-9H-芴-2,7-二基）双（噻吩-5,2-二基））双（2,5-与BPDPP具有相同化学结构的二辛基-3-（噻吩-2-基）吡咯并[3,4-c]吡咯-1,4（2H，5H）-二酮））除了B←N单元是通过相同的偶联反应合成的。这些小分子的吸收光谱和循环伏安分析表明，B←N单元通过保持较大的氧化电位来减小BPDPP的带隙。结果，BPDPP和PC ₇₁ BM的共混膜在1个日光浸泡测试315小时后仍保持了初始吸收强度的87.4％。BPDPP的光稳定性明显高于P3HT：PC ₇₁ BM的共混膜，后者仅在光浸泡23 h后才保持初始吸收强度的19.8％。